The present invention relates to a cross shaft (a spider) and a cross shaft joint.
In a torque transmission system in a vehicle or the like, a cross shaft joint has been generally employed for the purpose of connecting two rotary shafts which are provided in a non-coaxial manner, or which are provided so as to be tilted in a non-coaxial manner.
In this cross shaft joint, there has been a tendency that contact face pressure of rollers at a distal end of a trunnion of the cross shaft may increase at a time of torque transmission, and the rollers may break down where high load is applied. To avoid such break down of the rollers, the rollers are arranged in a plurality of rows in an axial direction in an annular space between an outer peripheral face of the trunnion and an outer ring cup of the roller bearing, and diameters of the rollers in respective rows are made successively larger from the distal end of the trunnion to the root thereof, thereby to substantially equalize the contact face pressure exerted on the rollers in the respective rows, at the time of torque transmission (See JP-A-11-51073, for example).
In the above described related art, the more the load at the time of torque transmission increases, the larger differences must be made between the diameters of the rollers in the respective rows. In this case, because radial clearances of the rollers which are reduced in diameter with respect to the trunnion will be made larger, the rollers become liable to skew.
Moreover, it has been proposed that a recess substantially in a shape of a frustum of a cone is formed at an end face of the trunnion of the cross shaft to reduce bending rigidity of the trunnion. For this purpose, there is an example that the trunnion will be flexed at the time of torque transmission, whereby deflection of bending stress to the root of the trunnion will be reduced (See JU-A-61-141819, for example).
However, in the above described related art, it is concerned that in case where a large recess is formed, rigidity of the trunnion with respect to the load at the time of torque transmission may be insufficient. This is an area for further improvement.